Fire alarm



1969 s. FRANKFURT' 3,475 7 FIRE ALARM Filed Jun 22, 1966 H 38 42 gig;

I E v 44 I 24 INVENTOR. SAN/30R FRANKFURT United States Patent 3,475,744FIRE ALARM Sandor Frankfurt, 13534 Cedar Road, Cleveland, Ohio 44118Filed June 22, B66, Ser. No. 559,491 Int. Cl. GtlSb 21/00 US. Cl.340-2271 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to afire and burglar alarm or other electrical signal systems using athermal responsive device that can be mechanically actuated.

Signal systems using thermal responsive devices are especially useful asfirst alarms. In these systems an audible or visual signal, or both, isactuated in response to a change in temperature, such as an increase intemperature to an abnormally high level, indicating the existence of afire or other abnormal condition.

Signal systems for burglar alarms are often mechanically actuated.Normally, an audible signal is created when the alarm is tripped, aswhen a door, window or compartment lid is opened.

For many uses and in many installations it is advantageous to provide aself-contained, independent signal system. Such a system is operableeven though there may be a power failure. It is also conveniently usedin buildings, 'vehicles or other areas where central power may not beavailable.

Small and inexpensive alarm systems are particularly advantageous. Anumber of such systems can be located unobtrusively in a variety ofdifferent places to act independently. With a large number of thermalsensitive systems at various locations, a fire is detected immediatelyat its source of origin. As is well known, early discovery and controlof a fire is often the difference between minor damage and totaldestruction of a building. Similarly, a separate burglar alarm at eachentrance of a building indicates the location of disturbance. A small,self contained alarm can conveniently be used to protect cars, boats,trailers or compartments within such vehicles.

One problem of many fire alarm systems is that they shut off after onceactuated if the temperature falls below the triggering temperature.Thus, if a fire should die down or shift, the alarm often shuts off. Asa result, the fire may smolder and later flare up in a differentlocation or in the same location with renewed vigor if the initial alarmsignal is not observed. It is also desirable that a burglar alarm remainactuated even if the door or window that is opened to trip the alarm issubsequently closed.

One proposed solution to some of the above problems, in connection witha fire alarm system is disclosed and claimed in my US. Patent No.2,762,887. As disclosed in that patent, a thermal responsive device isprovided with a hook. When the device is actuated by an increase intemperature, the hook engages a prong, which holds the device actuated.

The present invention provides the advantageous features of my earlierinvention, but in an improved manner and in an arrangement that providesan extremely ice compact, self-contained signal system that can be usedas both a fire alarm and burglar alarm. In addition, the alarm of thepresent invention can be conveniently tested and reset withoutdisassembly.

Briefly, this invention utilizes a resilient thermally distortableelement, such as a bimetallic strip, that is movable between twopositions in response to a change in temperature to a predeterminedlevel. Distortion of the thermally responsive element causes the elementto complete an electrical circuit that energizes a signal device. Apermanent magnet is positioned to retain the thermally distortableelement in the position to which it moves in response to the change intemperature. The magnet is of sufficient strength to retain the elementin position to maintain the circuit closed, notwithstanding a subsequentchange in temperature. As a result, the signal remains energized oncethe predetermined temperature is reached.

An important feature of this invention resides in the construction andarrangement of the thermally distortable element with respect to thehousing for the signal system. A portion of the bimetallic thermalresponsive element extends through the housing and moves from a firstposition to a second position in response to an increase in temperaturefrom below a predetermined temperature level to the predeterminedtemperature level. At the second position, the bimetallic elementcompletes an electrical circuit and operates the signal. The portion ofthe bimetallic element that extends through the housing permits thealarm to be mechanically actuated from outside the housing independentlyof any change in temperature. When the extending portion of thebimetallic element is moved from one position to another, whethermechanically or manually, the electrical circuit is completed. Anextending strip from a door or window can be used to mechanically movethe element when the protected door or window is opened, causing thealarm to operate. Also, the strip can be manually moved to test whetherthe alarm is functoning properly. The actuated alarm is turned off andreset by manually moving the extending portion of the bimetallic elementaway from the permanent magnet.

Accordingly, it is an object of this invention to provide an improvedthermal responsive and mechanically actuatable device in the form of anindependent signal system that once energized remains energized and thatcan be conveniently tested and reset.

These and other objects, features and advantages of this invention willbecome better understood by reference to the following detaileddescription, when taken in conjunction with the accompanying drawings,in which:

FIGURE 1 is a diagrammatic, perspective view of a signal systemconstructed in accordance with the present invention, showing the outerhousing and the manner in which the thermal responsive element extendsthrough the housing to facilitate testing and resetting;

FIGURE 2 is a top plan view of the signal system with one half of thehousing removed, showing the construc tional details and arrangement ofthe elements of the system;

FIGURE 3 is a sectional view of the system of FIG URE 2, taken along thelines 3-3 and looking in the direction of the arrows;

FIGURE 4 is a wiring diagram of the alarm system; and

FIGURE 5 is a partial enlarged longitudinal sectional view of thebimetallic element and permanent magnet of the alarm system.

Referring now to the drawings, the self-contained signal system isindicated generally at 10. It includes anouter housing 12 having twoportions 12a, 12b that interconnect to provide a box-like constructionin which the operative elements of the alarm system are contained. Afront surface 13 and a rear surface 14 of the housing 12 include slotopenings 16 to permit an audible signal from within the housing to beemitted. Fin-like members 18a and 19a on the housing portion 12a, and18b and 19b on housing portion 12b extend from the housing 12 about thefront, back and side surfaces. These members assure that the openings 16will be spaced from the wall, shelf, or other surrounding environment sothat a clear, audible sound will be emitted from the housing 12 nomatter how it is oriented. Preferably, the housing is formed ofelectrically non-conducting material, such as plastic or wood. The twohousing portions 12a, 12b are secured together by detents 20 on oppositeends of housing portion 12a. These detents extend into portion 12b andare received by indentations (not shown) formed in the inside surface ofthe end walls of housing 12b.

An opening 22 is provided in the housing portion 12a to permit one endof a bimetallic thermal responsive strip 24 to extend from the inside ofthe housing to the outside. The opening 22 is large enough to permitmovement of the bimetallic strip 24 in a direction toward and away fromthe front surface 13 of the housing 12.

As best shown in FIGURES 2, 3 and 5, the bimetallic thermal responsivestrip 24 in undistorted condition at room temperature (68 degreesFahrenheit) is essentially flat and straight, and extends at a slightangle with respect to front surface 13. The strip 24 is anchored at oneend by a screw 26 to a support block 28 formed in the housing portion12a. As shown in FIGURE 3, the support block 28 is formed with aninclined upper surface 29 to orient the strip 24 at the desired angle.

The free end of the strip 24 extends through opening 22 and supports acap 30. The cap 30 includes indicia on each side. One side says test,indicating that movement of the strip 24 by manual pressure against thestrip on that side of the cap will cause the alarm to operate. Theindicia stop is imprinted on the opposite side of the cap 30 to indicatethat pressure applied manually on this of the cap stops the alarm.

A signal device, such as a buzzer 34 is contained within the housing 12,being secured by screws 36 to the housing portion 12a. An electricallyconductive strip 38 extends from a contact 39 of the buzzer 34 to alocation beneath the bimetallic thermal responsive strip 24, adjacentthe opening 22 in the housing 12. A screw 40 secures a permanent magnet42, such as an alnico magnet, and the electrically conductive strip 38together on a support block 44 of the housing 12. As best shown inFIGURE 3, the magnet 42 is normally spaced from the bimetallic strip 24.

An insulated wire connector 45 extends from a second terminal of thebuzzer 34 to a bowed strip of spring metal 46, preferably of copper orcopper alloy, that forms a base plate for a battery 48. The strip ofmetal 46 is located adjacent one corner of the housing 12a and held in abowed condition by a partial partition 50. The partition 50 and a secondpartition 51 locate or cradle the bottom end of the battery 48inposition adjacent the'bowed strip of metal 46. As shown in FIGURE 2, thebattery 48, which is a standard type D 1.5 volt dry-cell, extends acrossone end of the housing 12. Additional contoured partitions 52, 53 formedin the housing portion 12a receive and locate the anodeend of thebattery 48;:

A spring clip in the form of an electrically conductive wire 56 isfastened to the support block 28 of thehousing 12a and held inelectrical contact with the bimetallic strip 24 by the screw 26. Thespring clip 56 includes an angui 4 sion, brass expanding at a muchgreater rate than steel for a given rise in temperature. The two metalsare laminated to provide the strip 24 with the steel portion 24aadjacent the magnet 42 and the brass portion 24b away from the magnet.With this arrangement, an increase in ambient temperature causes thestrip 24 to bow or deflect toward the magnet '42 due tothe increasedexpansion of the brass portion. Upon suflicient deformation ofthe strip24, the steel portion 24a comesfinto direct contact with the magnet 42so that the magnet will., hbld,the strip 24 in deformed position even ifthe temperature subsequently decreases. t

The electrical circuitry is diagrammatically "shown in FIGURE 4 of thedrawings. A series circuit is provided in which the anode of the battery48 is connected by spring clip 56 to the bimetallic strip 24, whichfunctions as a switch. The cathode side of the battery 48. is connectedby wire 45 to one terminal of the buzzer 34. The second terminal of thebuzzer 34 is connected-by strip 38 to the permanent magnet 42. Themagnet 42 and the bimetallic strip 24 act as spaced contacts which, whenclosed, complete the circuit.

In operation, the bimetallic thermal responsive strip 24 is normally ina straights configuration at room temperature (68 degrees Fahrenheit)and-spaced from'the permanent magnet 42. The spacing is suflicient thatthe attractive force of the magnet 42 will not draw the strip 24 intocontact with the magnet. The electrical circuit shown in FIGURE 4 istherefore normally opened and the buzzer 34 is inoperative. When theambient temperature of the environment in which thebimetallic thermalresponsive strip 24 is located increases, the strip 24 bends or deflectsin a direction toward the permanent magnet 42.

The strip 24 is constructed and arranged relative to the magnet 42 sothat it bends into contact with the magnet when the ambient temperaturereaches a predetermined level, such as 136 degrees Fahrenheit. Thetemperature level at which contact is made and the buzzer 34 operatedmay, of course, be varied by adjusting the initial gap between thebimetallic strip 24 and the magnet 42 or by varying the expansioncharacteristics of the strip itself.

The extending end of the strip 24 is also constructed and arranged to beoperable by a tripping mechanism, such as an extending finger (notshown) attached to a movable member such as a window or door. When thewindow or door is opened, movement of the finger contacts the cap 30 onthe end of the bimetallic strip and moves the strip into contact withthe magnet 42.

Once contact is made between the bimetallicstrip 24 and the permanentmagnet 42, a circuit is completed from the battery 48 through the buzzer34, the magnet 42 and the bimetallic strip 24 to energize the buzzer 34.The magnet 42 is selected of suflicient attractive force to overcome theresiliency of the strip 24,that tendsto return the strip to its initialposition, spaced from the magnet, when at room temperature. In this way,the circuit is held closed by the magnet 42, notwithstanding'asubsequent decrease in temperature or a subsequent closing ofthedooror'window if the alarm is mechanically "tripped. As aresult, thebuzzer will provide an indication that a' certain temperature level wasreached or that a door br-v'vindowwas opened, even if the alarm isnot'heard immediately'and even if the cause of setting off the alarm iseliminated. Moreover, even ifthe battery shouldrun down-before thesignal is heard, the position of thestri'p '24 in contact with themagnet 42 'indicates'that the alarm was at one time actuated.

To reset the alarm after ithasbeen actuated, the portion of thebimetallic strip 24 extending from the housing 12 is merely lifted awayfrom the magnet 42. If thetemperature is below the tripping temperatureof the alarm, the strip will remain out of contact with the magnet .42,in condition to function again as an alarm, Thus, there is no need todisassemble the device or to replace parts of the mechanism in order toreset the alarm.

Periodically, the signal system is tested to assure that the battery 48has not lost its power and to determine that other components areproperly functioning. This can be conveniently accomplished withoutopening the housing 12 by pressing the extending portion of the strip 24into contact with the magnet 42, causing the buzzer 34 to be energized.If the test is satisfactory, the strip 24 is then lifted from the magnet42, and the device is again ready to function. With this construction, asignal system is provided that functions as both a fire and burglaralarm, that is small and self-contained, and that uses a permanentmagnet as an inexpensive and convenient means to hold the alarmenergized and to facilitate the testing and resetting of the circuitwithout disassembly.

What is claimed is:

1. An independent signal system comprising:

(a) a signal device for producing a sensible signal when electricallyenergized,

(b) an electrical circuit for connecting the signal device to a sourceof electrical current,

(c) two normally spaced electrical contacts forming a part of theelectrical circuit, adapted when electrically connected to operate thesignal device through the electrical circuit,

(d) thermal responsive imeans movable mechanically and in response totemperature changes, for electrically connecting said two contacts inresponse to movement thereof,

(e) means, including a permanent magnet, to maintain the thermalresponsive means in a position electrically connecting the two contactsindependent of any change in temperature, once it has moved to such aposition,

(f) a housing enclosing the signal device, electrical circuit,electrical contacts and thermal responsive means, with an openingthrough which a portion of said thermal responsive means extends formechanical or manual engagement and which permits movement of saidthermal responsive means between a position in which the said contactsare electrically isolated and-a position in which the said contacts areelectrically connected by said thermal responsive means,

(g) whereby the signal system functions in response to either a changein temperature or mechanical actuation externally of said housing andcan be manually tested and reset without disassembly.

2. The system of claim 1 wherein the thermal responsive means is abimetallic element that distorts in response to temperature changes.

3. The system of claim 2 wherein the signal device is an audible alarm;a battery contained within the housing act as the source of current; thebimetallic element is essentially straight at ambient room temperature,includes at least one metal that has ferromagnetic properties positionedto contact the magnet when the element is subjected to the predeterminedtemperature level, and forms one of the normally spaced contacts; andthe permanent magnet is fixed relative to the housing, forms the otherof the normally spaced contacts, and has sufiicient magnetic attractionto hold the bimetallic element in contact with the magnet once contactis made, independent of subsequent changes in temperature.

4. The system of claim 3 wherein the housing includes openings to emitaudible sounds and has projections that maintain the openings spacedfrom any large, flat, adjacent surface.

References Cited UNITED STATES PATENTS 2,806,108 9/1957 Babson340--227.1 X 2,832,949 4/1958 Pivetz 340227.1 2,839,639 6/1958Adlerstein 337-366 X JOHN W. CALDWELL, Primary Examiner D. L. TRAFTON,Assistant Examiner U.S. Cl. X.R.

